Base station and user terminal for performing measurement and communication in unlicensed frequency bands

ABSTRACT

A user terminal according to an embodiment comprises a receiver; and a controller. The receiver receives, from a base station, a message including first and second information. The first information is information regarding to a configuration for reporting a power measured by the user terminal in the unlicensed band, and includes period information indicating a period of a measurement in the unlicensed band. The second information is information regarding to a configuration of carrier aggregation. The controller periodically measures the power in the unlicensed band according to the period information; reports to the base station on information classified according to the measured power as information indicating the measured power, based on the first information; performs a configuration for using the unlicensed band as a secondary carrier in the carrier aggregation, based on the second information; and communicates a communication with the base station by using the secondary carrier.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation based on PCT Application No.PCT/JP2015/072184 filed on Aug. 5, 2015, which claims the benefit ofJapanese Patent Application No. 2014-159386 filed on Aug. 5, 2014,entitled “BASE STATION AND USER TERMINAL,” the contents of which areincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present application relates to a user terminal capable of performingcommunication in a specific frequency band and a base station capable ofcommunicating with the user terminal.

BACKGROUND ART

In 3GPP (3rd Generation Partnership Project), which is a project aimingto standardize a mobile communication system, specifications are beingdesigned to enhance LTE (Long Term Evolution) in order to comply withthe rapidly increasing traffic demands (for example, see 3GPP TechnicalSpecification “TS 36.300 V12.0.0” January, 2014).

At the same time, a specific frequency band available without a license(Unlicensed Band/Unlicensed Spectrum) has attracted attention. As ameans for responding to a rapidly increasing traffic demand in a mobilecommunication system, it may be possible to utilize the above-describedspecific frequency band for the mobile communication.

SUMMARY

A user terminal according to an embodiment is configured to communicateby using an unlicensed band. The user terminal comprises a receiver; anda controller. The receiver is configured to receive, from a basestation, a message including first information and second information.The first information is information regarding to a configuration forreporting a power measured by the user terminal in the unlicensed band.The first information includes period information indicating a period ofa measurement in the unlicensed band. The second information isinformation regarding to a configuration of carrier aggregation. Thecontroller is configured to: periodically measure the power in theunlicensed band according to the period information; report to the basestation on information classified according to the measured power asinformation indicating the measured power, on a basis of the firstinformation; perform a configuration for using the unlicensed band as asecondary carrier in the carrier aggregation, on a basis of the secondinformation; and communicate a communication with the base station byusing the secondary carrier.

A processor according to an embodiment is a processor for controlling auser terminal configured to communicate by using an unlicensed band. Theprocessor is configured to receive a message including first informationand second information. The first information is information regardingto a configuration for reporting a power measured by the user terminalin the unlicensed band. The first information includes periodinformation indicating a period of a measurement in the unlicensed band.The second information is information regarding to a configuration ofcarrier aggregation. The processor is configured to: periodicallymeasure the power in the unlicensed band according to the periodinformation; report to the base station on information classifiedaccording to the measured power as information indicating the measuredpower, on a basis of the first information; perform a configuration forusing the unlicensed band as a secondary carrier in the carrieraggregation, on a basis of the second information; and communicate acommunication with the base station by using the secondary carrier.

A base station according to an embodiment comprises: a transmitter; areceiver; and a controller. The transmitter is configured to transmit amessage including first information and second information, to a userterminal configured to communicate by using an unlicensed band. Thefirst information is information regarding to a configuration forreporting a power measured by the user terminal in the unlicensed band.The first information includes period information indicating a period ofa measurement in the unlicensed band. The second information isinformation regarding to a configuration of carrier aggregation. Thereceiver configured to receive, from the user terminal, informationclassified according to the measured power as information indicating themeasured power. The controller configured to perform a communicationwith the user terminal by using the unlicensed band as a secondarycarrier in the carrier aggregation.

A processor according to an embodiment is a processor for controlling abase station. The processor is configured to: transmit, a messageincluding first information and second information, to a user terminalconfigured to communicate by using an unlicensed band. The firstinformation is information regarding to a configuration for reporting apower measured by the user terminal in the unlicensed band. The firstinformation includes period information indicating a period of ameasurement in the unlicensed band. The second information isinformation regarding to a configuration of carrier aggregation. Theprocessor is configured to: receive, from the user terminal, informationclassified according to the measured power as information indicating themeasured power; and perform a communication with the user terminal byusing the unlicensed band as a secondary carrier in the carrieraggregation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of an LTE system according to anembodiment.

FIG. 2 is a block diagram of a UE according to the embodiment.

FIG. 3 is a block diagram of an eNB according to the embodiment.

FIG. 4 is a protocol stack diagram according to the embodiment.

FIG. 5 is a configuration diagram of a radio frame according to theembodiment.

FIG. 6 is a diagram for describing communication in a specific frequencyband according to the embodiment.

FIG. 7 is a sequence diagram for describing an operation according to afirst embodiment.

FIG. 8 is a sequence diagram for describing an operation according to amodification 1 of the first embodiment.

FIG. 9 is a sequence diagram for describing an operation according to amodification 2 of the first embodiment.

FIG. 10 is a sequence diagram for describing an operation according to asecond embodiment.

FIG. 11 is a sequence diagram for describing an operation according to amodification 1 of the second embodiment.

FIG. 12 is a sequence diagram for describing an operation according to amodification 2 of the second embodiment.

FIG. 13 is a sequence diagram for describing an operation according to amodification 3 of the second embodiment.

FIG. 14 is a sequence diagram for describing an operation according to amodification 4 of the second embodiment.

DESCRIPTION OF THE EMBODIMENT

[Overview of Embodiment]

A base station according to a first present embodiment is capable ofcommunication with a user terminal used in a cellular communicationsystem. The base station comprises a controller configured to acquire afirst measurement report indicating an interference state, measured bythe user terminal, in a specific frequency band that can be utilizedwithout a license, and to allocate, on the basis of the firstmeasurement report, a time-frequency resource in the specific frequencyband to the user terminal.

In a first embodiment, the controller utilizes a general frequency bandwhich is a frequency band different from the specific frequency band andin which a license is granted to a cellular network operator, so as toacquire the first measurement report.

In a first embodiment, the controller further acquires a secondmeasurement report indicating an interference state in the specificfrequency band measured by a cell of the specific frequency band. Thecontroller allocates, on the basis of the first measurement report andthe second measurement report, the time-frequency resource.

The base station according to a first embodiment further comprises: atransmitter configured to transmit configuration information instructinga timing at which the user terminal measures the interference state. Thecontroller allocates the time-frequency resource so that the userterminal does not perform cellular communication at the timing.

A user terminal according to a first embodiment is used in a cellularcommunication system. The user terminal comprises: a controllerconfigured to perform control to measure an interference state in aspecific frequency band that can be utilized without a license. Thecontroller performs control to notify a base station configured toallocate, to the user terminal, a time-frequency resource in thespecific frequency band, of a measurement report indicating theinterference state.

In a first embodiment, the controller utilizes a general frequency bandwhich is a frequency band different from the specific frequency band andin which a license is granted to a cellular network operator, so as toperform the control to notify the measurement report.

A user terminal according to a first embodiment further comprises areceiver configured to receive configuration information instructing atiming at which the user terminal measures the interference state. Thecontroller performs control to measure the interference state at atiming instructed by the configuration information.

A base station according to a second embodiment is capable ofcommunication with a user terminal used in a cellular communicationsystem. The base station comprises: a controller configured to performcontrol to stop allocation of a time-frequency resource in a specificfrequency band to the user terminal, on the basis of informationtransmitted from the user terminal if reception quality of the userterminal in the specific frequency band that can be utilized without alicense is lower than a threshold value. The information is transmittedby utilizing a general frequency band which is a frequency banddifferent from the specific frequency and in which a license is grantedto a cellular network operator.

In a second embodiment, the information is a notification to request astop of communication in the specific frequency band.

In a second embodiment, the information is a negative acknowledgmentindicating that the user terminal has not properly received data byutilizing the specific frequency band. The controller performs controlto stop allocation of the time-frequency resource in accordance with areception state of the negative acknowledgment.

In a second embodiment, the controller performs control, on the basis ofthe information, to transmit, to another base station configured toperform communication with the user terminal in the specific frequencyband, an instruction to stop transmission to the user terminal.

In a second embodiment, the controller performs control, on the basis ofthe information, to transmit, to the user terminal, a measurementinstruction of an interference state in the specific frequency band, byutilizing the general frequency band.

In a second embodiment, the controller acquires, from the user terminal,a request for starting communication in the specific frequency band, andon the basis of the request, performs control to restart the allocationof the time-frequency resource to the user terminal.

A base station according to a second embodiment is capable ofcommunication with a user terminal used in a cellular communicationsystem. The base station comprises: a controller configured to controlcommunication with the user terminal in a specific frequency band thatcan be used without a license. The controller transmits, if receptionquality of the user terminal in the specific frequency band is lowerthan a threshold value, information indicating that the receptionquality of the user terminal is lower than the threshold value, toanother base station via a backhaul. The other base station is a basestation capable of performing communication with the user terminal byutilizing a general frequency band in which a license is granted to acellular network operator.

In a second embodiment, the information is used as a trigger for causingthe user terminal to measure an interference state in the specificfrequency band.

A base station according to a second embodiment is capable ofcommunication with a user terminal used in a cellular communicationsystem. The base station comprises: a controller configured to allocate,to the user terminal, a time-frequency resource in a specific frequencyband that can be used without a license. The controller performs controlto stop, if reception quality of the user terminal in the specificfrequency band is lower than a threshold value, the allocation of thetime-frequency resource.

A user terminal according to a second embodiment is used in a cellularcommunication system. The user terminal comprises: a controllerconfigured to control communication in a specific frequency band thatcan be used without a license. The controller performs control tonotify, if reception quality in the specific frequency band is lowerthan a threshold value, a base station of predetermined information byutilizing a general frequency band that is a frequency band differentfrom the specific frequency band. The base station is a base stationconfigured to allocate a time-frequency resource in the specificfrequency band to the user terminal. The general frequency band is afrequency band in which a license is granted to a cellular networkoperator.

In a second embodiment, the predetermined information is a negativeacknowledgment indicating that it is not possible to have properlyreceived data by utilizing the specific frequency band.

In a second embodiment, the predetermined information is a notificationto request a stop of the communication in the specific frequency band.

In a second embodiment, in accordance with the number of times in whichit is not possible to have properly received data by utilizing thespecific frequency band, the controller performs control to startmeasurement of an interference state in the specific frequency band.

The user terminal according to a second embodiment comprises: a receiverconfigured to receive, by utilizing the general frequency band, ameasurement instruction, from the base station, for an interferencestate in the specific frequency band. The controller performs control,on the basis of the measurement instruction, to start measurement of theinterference state in the specific frequency band.

In a second embodiment, the controller performs control to transmit, ifthe communication in the specific frequency band is stopped, a requestto start the communication in the specific frequency band, on the basisof a measurement result of the interference state.

It is noted that a “base station” as used in the claims is a conceptalso including not only a general base station (a so-called eNB) butalso an RRH base station (Remote Radio Head).

[First Embodiment]

Hereinafter, the embodiment in a case where a content of the presentapplication is applied to an LTE system will be described.

(System Configuration)

FIG. 1 is a configuration diagram of an LTE system according to anembodiment. As shown in FIG. 1, the LTE system according to theembodiment includes UEs (User Equipments) 100, E-UTRAN (EvolvedUniversal Terrestrial Radio Access Network) 10, and EPC (Evolved PacketCore) 20.

The UE 100 corresponds to a user terminal. The UE 100 is a mobilecommunication device and performs radio communication with a connectedcell (a serving cell). Configuration of the UE 100 will be describedlater.

The E-UTRAN 10 corresponds to a radio access network. The E-UTRAN 10includes eNBs 200 (evolved Node-Bs). The eNB 200 corresponds to a basestation. The eNBs 200 are connected mutually via an X2 interface.Configuration of the eNB 200 will be described later.

The eNB 200 manages a cell or a plurality of cells and performs radiocommunication with the UE 100 that establishes a connection with thecell of the eNB 200. The eNB 200, for example, has a radio resourcemanagement (RRM) function, a function of routing user data, and ameasurement control function for mobility control and scheduling. It isnoted that the “cell” is used as a term indicating a minimum unit of aradio communication area, and is also used as a term indicating afunction of performing radio communication with the UE 100.

The EPC 20 corresponds to a core network. A network of the LTE system (aLTE network) is configured by the E-UTRAN 10 and the EPC 20. The EPC 20includes MME (Mobility Management Entity)/S-GW (Serving-Gateway) 300.The EPC 20 may include an OAM (Operation and Maintenance).

The MME performs various mobility controls and the like, for the UE 100.The S-GW performs control to transfer user data. The MME/S-GW 300 isconnected to the eNB 200 via an S1 interface.

The OAM is a server apparatus managed by an operator and performsmaintenance and monitoring of the E-UTRAN 10.

FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100includes an antenna 101, a radio transceiver 110, a user interface 120,GNSS (Global Navigation Satellite System) receiver 130, a battery 140, amemory 150, and a processor 160. The UE 100 may not have the GNSSreceiver 130. Furthermore, the memory 150 may be integrally formed withthe processor 160, and this set (that is, a chip set) may be a processor160′ constituting the controller.

The antenna 101 and the radio transceiver 110 are used to transmit andreceive a radio signal. The radio transceiver 110 converts a basebandsignal (a transmission signal) output from the processor 160 into theradio signal, and transmits the radio signal from the antenna 101.Furthermore, the radio transceiver 110 converts a radio signal (areception signal) received by the antenna 101 into the baseband signal,and outputs the baseband signal to the processor 160.

The radio transceiver 110 comprises a radio transceiver 110A and a radiotransceiver 110B. The radio transceiver 110A transmits and receives aradio signal by utilizing the general frequency band, and the radiotransceiver 110B transmits and receives a radio signal by utilizing thespecific frequency band.

The user interface 120 is an interface with a user carrying the UE 100,and includes, for example, a display, a microphone, a speaker, variousbuttons and the like. The user interface 120 receives an operation froma user and outputs a signal indicating the content of the operation tothe processor 160. The GNSS receiver 130 receives a GNSS signal in orderto obtain location information indicating a geographical location of theUE 100, and outputs the received signal to the processor 160. Thebattery 140 accumulates a power supplied to each block of the UE 100.

The memory 150 stores a program to be executed by the processor 160 andinformation to be used for a process by the processor 160. The processor160 includes a baseband processor that performs modulation anddemodulation, encoding and decoding and the like on the baseband signal,and a CPU (Central Processing Unit) that performs various processes byexecuting the program stored in the memory 150. The processor 160 mayfurther include a codec that performs encoding and decoding on sound andvideo signals. The processor 160 corresponds to a controller andexecutes various processes and various communication protocols describedlater.

FIG. 3 is a block diagram of the eNB 200. As shown in FIG. 3, the eNB200 includes a plurality of antennas 201, a radio transceiver 210, anetwork interface 220, a memory 230, and a processor 240. It is notethat the memory 230 may be integrated with the processor 240, and thisset (that is, a chipset) may be a processor 240′ constituting thecontroller.

The antenna 201 and the radio transceiver 210 are used to transmit andreceive a radio signal. The radio transceiver 210 converts a basebandsignal (a transmission signal) output from the processor 240 into theradio signal, and transmits the radio signal from the antenna 201.Furthermore, the radio transceiver 210 converts a radio signal (areception signal) received by the antenna 201 into the baseband signal,and outputs the baseband signal to the processor 240.

The network interface 220 is connected to the neighbor eNB 200 via theX2 interface and is connected to the MME/S-GW 300 via the S1 interface.The network interface 220 is used in communication performed on the X2interface and communication performed on the S1 interface.

The memory 230 stores a program to be executed by the processor 240 andinformation to be used for a process by the processor 240. The processor240 includes the baseband processor that performs modulation anddemodulation, encoding and decoding and the like on the baseband signaland a CPU that performs various processes by executing the programstored in the memory 230. The processor 240 corresponds to a controllerand executes various processes and various communication protocolsdescribed later.

FIG. 4 is a protocol stack diagram of a radio interface in the LTEsystem. As shown in FIG. 4, the radio interface protocol is classifiedinto a layer 1 to a layer 3 of an OSI reference model, wherein the layer1 is a physical (PHY) layer. The layer 2 includes MAC (Medium AccessControl) layer, RLC (Radio Link Control) layer, and PDCP (Packet DataConvergence Protocol) layer. The layer 3 includes RRC (Radio ResourceControl) layer.

The PHY layer performs encoding and decoding, modulation anddemodulation, antenna mapping and demapping, and resource mapping anddemapping. Between the PHY layer of the UE 100 and the PHY layer of theeNB 200, user data and a control signal are transmitted through thephysical channel.

The MAC layer performs priority control of data, and a retransmissionprocess and the like by hybrid ARQ (HARQ). Between the MAC layer of theUE 100 and the MAC layer of the eNB 200, user data and a control signalare transmitted via a transport channel. The MAC layer of the eNB 200includes a scheduler to decide (schedule) a transport format of anuplink and a downlink (a transport block size, a modulation and codingscheme) and an allocated resource block to the UE 100.

The RLC layer transmits data to an RLC layer of a reception side byusing the functions of the MAC layer and the PHY layer. Between the RLClayer of the UE 100 and the RLC layer of the eNB 200, user data and acontrol signal are transmitted via a logical channel.

The PDCP layer performs header compression and decompression, and cipherand decipher.

The RRC layer is defined only in a control plane handling a controlsignal. Between the RRC layer of the UE 100 and the RRC layer of the eNB200, a control signal (an RRC message) for various types ofconfiguration is transmitted. The RRC layer controls the logicalchannel, the transport channel, and the physical channel in response toestablishment, re-establishment, and release of a radio bearer. When aconnection (an RRC connection) is established between the RRC of the UE100 and the RRC of the eNB 200, the UE 100 is in an RRC connected state,and when the connection is not established, the UE 100 is in an RRC idlestate.

NAS (Non-Access Stratum) layer positioned above the RRC layer performssession management, mobility management and the like.

FIG. 5 is a configuration diagram of a radio frame used in the LTEsystem. In the LTE system, OFDMA (Orthogonal Frequency DivisionMultiplexing Access) is employed in a downlink (DL), and SC-FDMA (SingleCarrier Frequency Division Multiple Access) is employed in an uplink(UL), respectively.

As shown in FIG. 5, the radio frame is configured by 10 subframesarranged in a time direction. Each subframe is configured by two slotsarranged in the time direction. Each subframe has a length of 1 ms andeach slot has a length of 0.5 ms. Each subframe includes a plurality ofresource blocks (RBs) in a frequency direction, and a plurality ofsymbols in the time direction. Each resource block includes a pluralityof subcarriers in the frequency direction. A resource element isconfigured by one subcarrier and one symbol. Among radio resourcesallocated to the UE 100, a frequency resource is configured by aresource block and a time resource is configured by a subframe (orslot).

(Communication in Specific Frequency Band)

Communication in a specific frequency band according to the presentembodiment will be described below with reference to FIG. 6. FIG. 6 is adiagram for describing communication in a specific frequency bandaccording to the present embodiment.

As illustrated in FIG. 6, the UE 100 is capable of performingcommunication not only in a general frequency band in which a cellularnetwork operator is granted with a license (Licensed band/Licensedspectrum) but also in a specific frequency band available without alicense (Unlicensed Band/Unlicensed spectrum).

Specifically, firstly, the UE 100 is capable of performing communicationin a specific frequency band by Carrier Aggregation (CA).

In the CA, in order to ensure a backward compatibility with the LTEwhile realizing an enhanced broadband, a carrier (a frequency band) inthe LTE is positioned as a component carrier, and the UE 100 performscommunication by simultaneously using a plurality of component carriers(a plurality of serving cells). In the CA, a cell that providespredetermined information when the UE starts the RRC connection isreferred to as primary cell (PCell). For example, the primary cellprovides NAS mobility information at the time of RRC connectionestablishment/re-establishment/handover (for example, TAI) and providessecurity information at the time of RRC connectionre-establishment/handover. On the other hand, a supplementary servingcell forming a pair with the primary cell is referred to as a secondarycell (SCell). The secondary cell is formed together with the primarycell.

If using the CA for communication in a specific frequency band, there isa case where the specific frequency band is utilized as the secondarycell. If the specific frequency band is utilized as the secondary cell,the secondary cell is referred to as a U-SCell, below.

Secondly, the UE 100 is capable of performing communication in thespecific frequency band by a dual connectivity (DC).

In the DC, the UE 100 is allocated with a radio resource from aplurality of eNBs 200. The DC may be referred to as an inter-eNB carrieraggregation (inter-eNB CA).

In the DC, out of a plurality of eNBs 200 that establish connection withthe UE 100, only a master eNB (MeNB) establishes an RRC connection withthe UE 100. On the other hand, out of the plurality of eNBs 200, asecondary eNB (SeNB) provides an additional radio resource to the UE 100without establishing the RRC connection with the UE 100. An Xn interfaceis set between the MeNB and the SeNB. The Xn interface is either an X2interface or a new interface.

In the DC, the UE 100 is capable of carrier aggregation in which N cellsmanaged by the MeNB and M cells managed by the SeNB are simultaneouslyutilized. Further, a group including the N cells managed by the MeNB iscalled a master cell group (MCG). Moreover, a group including the Mcells managed by the SeNB is called a secondary cell group (SCG).Further, out of the cells managed by the SeNB, a cell having a functionof receiving at least an uplink control signal (PUCCH) is referred to asa pSCell. The pSCell, which has several functions in much the same wayas the PCell, does not perform the RRC connection with the UE 100 anddoes not transmit the RRC message, either, for example. It is noted thatif the specific frequency band is utilized as the Scell, the Scell isreferred to as a U-SCell, and if the specific frequency band is utilizedas the pSCell, the Scell is referred to as a U-pSCell.

Here, it is assumed that as a mode of communication in the specificfrequency band, Licensed-Assisted Access (LAA) is utilized. In the LAA,a general frequency band is used as the primary carrier, and thespecific frequency band is used as the secondary carrier. The secondarycarrier may be a carrier for downlink and uplink, and may be a carrierdedicated to downlink.

Description proceeds below that (A) is a case where an eNB 200configured to manage a primary cell (primary carrier) is arranged with ascheduler (scheduling control device) and at least a specific controlsignal is exchanged by the primary carrier is an LAA case; (B) is a casewhere an eNB 200 configured to manage a secondary cell (secondarycarrier) is arranged with a scheduler and at least a specific controlsignal is exchanged by a primary carrier is a Standalone with LAA case;and (C) is a case where an eNB 200 configured to manage a secondary cell(secondary carrier) is arranged with a scheduler and a control signal isexchanged by a secondary carrier is a Standalone case (see FIG. 6).

The (A) LAA case includes a case where a specific frequency band isutilized as a secondary cell, in the CA, and a case where a specificfrequency band is utilized as a cell managed by an SeNB in the DC. If aneNB configured to manage a primary cell and an eNB configured to managea secondary cell are the same, the CA is utilized, and if an eNBconfigured to manage a primary cell and an eNB configured to manage asecondary cell are different, the DC is utilized.

The (B) Standalone with LAA case includes a case where a specificfrequency band is utilized as a cell manage by a SeNB in the DC.Specifically, there is a case where the SeNB manages a U-SCell includinga U-pSCell and a case where the same manages a U-pSCell (only), forexample.

The (C) Standalone case includes a case where a UE 100 performs, withoututilizing a general frequency band, communication in a specificfrequency band, e.g., a case where a specific frequency band is utilizedas a primary cell and a secondary cell in the CA.

Description proceeds that it is assumed where appropriate that anoperation by an eNB 200 is an operation by a cell managed by an eNB 200,below.

(Operation According to First Embodiment)

An operation according to the first embodiment will be described byusing FIG. 7. FIG. 7 is a sequence diagram for describing the operationaccording to the first embodiment. Here, the LAA case will be described.If the CA is utilized, below, a notification between a PCell and aU-SCell is performed within an eNB 200. On the other hand, if the DC isutilized, a notification between a PCell and a U-SCell and anotification between a PCell and a pSCell are performed via a backhaul(with or without wires) between the eNBs 200.

As illustrated in FIG. 7, in step S101, the Pcell transmits an RRCconnection reconfiguration message (RRC Connection Reconfiguration) tothe UE 100.

The RRC connection reconfiguration message includes configurationinformation (U-SCell add/feedback config.) for utilizing the specificfrequency band as the secondary carrier and/or for feeding back ameasurement result of an interference state in the specific frequencyband.

The configuration information may include any one of the followinginformation.

-   -   Information indicating a radio resource used by the UE 100 to        feed back the measurement result of the interference state    -   Information used by the UE 100 to instruct a timing for        measuring the interference state (for example, a measurement gap        (Gap) set to measure the interference state by the UE 100)    -   Information indicating a threshold value used when the UE 100        determines the interference

The UE 100 that has received the RRC connection reconfiguration messagechanges the configuration of the RRC connection with the PCell. Further,the UE 100 performs the configuration, on the basis of the configurationinformation included in the message. For example, the UE 100 performs,on the basis of the U-SCell add config., the configuration for utilizingthe specific frequency band as the secondary carrier (U-SCell).

It is noted that the PCell may transmit the configuration information byan SIB.

In step S102, the PCell transmits a U-cell activation message (U-cellActivate) to the UE 100.

In step S103, the UE 100 that has received the U-cell activationmessage, starts monitoring a downlink to perform communication with theU-SCell set on the basis of the U-SCell add config. That is, the UE 100activates the U-SCell, in response to reception of the U-cell activationmessage. Further, UE 100 activates (turns on) the radio transceiver 110Bif the radio transceiver 110B for specific frequency band has not beenactivated.

It should be noted that if setting a timer (Deactivation timer) forending the communication with the U-SCell, the UE 100 activates thetimer simultaneously of the activation of the U-SCell. If the timerexpires, the UE 100 deactivates the U-SCell (if a plurality of U-SCellsare activated, the UE 100 deactivates the U-SCell corresponding to thetimer). In this case, the UE 100 may turn the radio transceiver 110BOFF. Further, upon reception of the PDCCH indicating an uplink grant ora downlink assignment for communication with the U-SCell, the UE 100restarts the timer. Alternatively, the timer may be set to the PCell.

The timer may be a deactivation timer for the existing SCell(sCellDeactivationTimer), and may be a deactivation timer dedicated tothe U-SCell different from the sCellDeactivationTimer.

It is noted that, in response to reception of the configurationinformation in S101, the UE 100 may activate the U-SCell. The PCell mayomit transmission of the U-cell activation message.

In step S104, the UE 100 measures the interference state, on the basisof the configuration information included in the RRC connectionconfiguration message. As the measurement of the interference state, theUE 100 performs measurement on the interference applied to anotherdevice, rather than measurement on the interference received by the UE100 itself. That is, the UE 100 performs measurement for determiningwhether or not the UE 100 itself may perform transmission by apredetermined channel.

The UE 100 starts a carrier sense to measure the interference state inthe specific frequency band. Specifically, in order to search for a freechannel in the specific frequency band, the UE 100 starts measuringinterference power in the specific frequency band so as to monitor asurrounding communication situation. It is noted that if informationthat instructs the timing for measuring the interference state isincluded in the configuration information, the UE 100 measures theinterference state at a timing instructed by the configurationinformation.

The UE 100 determines that in the specific frequency band, a channel(e.g., a band unit, a sub-band unit, or a resource unit) in whichinterference power equal to or more than a threshold value (orInterference over Thermal Noise (IoT)) is measured as a used channel,and determines that other channels are free channels (or vacantresources). Further, the UE 100 may measure a reception time of theinterference power. The UE 100 may determine, if the reception time ofthe interference power is less than a threshold value, that the channelin which the interference power is measured is a free channel.

In the present embodiment, description proceeds with an assumption thatthe UE 100 determines that second and third channels are free channels,out of first to fourth channels configured by dividing the specificfrequency band into four parts in a frequency direction (see FIG. 7).

In step S105, the UE 100 is capable of transmitting (i.e., notifying),to the PCell or the pSCell, a measurement report (Free channel/resourcefeedback) indicating the interference state in the specific frequencyband. Therefore, the UE 100 transmits the measurement report byutilizing the general frequency band rather than the specific frequencyband. The PCell or the pSCell acquires the measurement report byutilizing the general frequency band. Thus, the PCell or the pSCell,which does not receive the interference from another radio deviceperforming communication in the specific frequency band, is capable ofreliably receive the measurement report. Further, the UE 100, which doesnot apply the interference to the other radio device even iftransmitting the measurement report, is capable of effectively utilizingthe specific frequency band. If receiving the measurement report, thepSCell (SeNB) notifies the PCell (MeNB) of the measurement report.

It is noted that the measurement report according to the presentembodiment differs from a CSI feedback in that the signal from theU-SCell is not subject to the measurement report and informationindicating the free channel is reported.

In the present embodiment, the UE 100 transmits, as the measurementreport, free channel information ({0,1,1,0}) indicating that second andthird channels are free channels.

Alternatively, the UE 100 may transmit, as the measurement report,information indicating the interference power itself to the PCell. Inthis case, the UE 100 may transmit information indicating that theinterference power is classified into Low, Mid, and High (e.g.,{3,0,1,3}), for example.

It is noted that the measurement report may include information on atime of the interference power (e.g., an interference power receptiontime and a time ratio of the interference power).

In step S106, the U-SCell notifies the PCell of the measurement reportindicating the interference state in the specific frequency bandmeasured by the (eNB configured to manage) U-SCell. The PCell acquiresthe measurement reports from the U-SCell.

The U-SCell performs a carrier sense for measuring the interferencestate in the specific frequency band in much the same way as the UE 100does. The U-SCell may regularly measure the interference state, and maystart the measurement by using, as a trigger, an instruction from thePCell.

In the present embodiment, description proceeds with an assumption thatthe U-SCell has notified, as the measurement report, free channelinformation ({1,0,1,1}) indicating that first, third, and fourthchannels are free channels.

In step S107, (a scheduling control device of) the PCell performsscheduling to allocate a time-frequency resource to the UE 100.Specifically, the PCell that has acquired the measurement report fromthe UE 100 and the measurement report from the U-SCell, performs, on thebasis of the acquired measurement report, scheduling so that the UE 100and the U-SCell do not receive nor apply, if performing communication inthe specific frequency band, the interference. The PCell, which iscapable of performing the scheduling, on the basis of both themeasurement reports from the transmission side and the reception side,is capable of further reducing the generation of the interference in thespecific frequency band. In the present embodiment, upon determination,on the basis of the measurement report, that the first, second, andfourth channels are the used channels and the third channel is the freechannel, the PCell allocates the third channel as the time-frequencyresource to the UE 100.

It is noted that if the UE 100 instructs the measurement on theinterference state at a regular timing, the Pcell allocates thetime-frequency resource so that the UE 100 does not perform cellularcommunication at the timing. That is, the PCell avoids the allocation ofthe time-frequency resource that overlaps the timing in the timedirection. As a result, the UE 100 is capable of ensuring themeasurement timing of the interference state, and thus, it is possibleto avoid a situation where it is not possible to measure theinterference state by the cellular communication.

Further, if the measurement report measured by another UE within thecoverage of the Pcell has been already acquired, the PCell is capable ofperforming, on the basis of the measurement report, the scheduling intaking into account a radio state in the specific frequency band of awhole of the coverage of the PCell. Thus, it is possible to solve ahidden terminal problem.

It is noted that instead of from another UE within the coverage of thePcell, the Pcell may acquire the measurement report from a radio device,the radio device being capable of measuring the interference state inthe specific frequency band within the coverage of the Pcell (e.g., aneNB configured to manage the specific frequency band, a wireless LANaccess point (AP), and an access controller (AC) that is a nodeconfigured to collectively manage a plurality of wireless LAN accesspoints).

It is noted that the PCell is capable of continuously performing thescheduling, on the basis of the acquired measurement report.

In step S108, the PCell notifies the U-SCell of the resource allocation(Resource Allocation) in step S107. In the present embodiment, theresource allocation is information indicating the third channel({0,0,1,0}).

In step S109, the PCell transmits to the UE 100 the resource allocation(Resource Allocation) in step S107, by utilizing the general frequencyband rather than the specific frequency band. Specifically, the PCelltransmits, to the UE 100, the resource allocation that is theinformation indicating the third channel ({0,0,1,0}) by the PDCCH in thegeneral frequency band.

In step S110, the U-SCell transmits, on the basis of the resourceallocation, the data to the UE 100 by utilizing the specific frequencyband, and the UE 100 receives, on the basis of the resource allocation,the data from the U-SCell.

In step S111, the UE 100 performs the carrier sense in order to measurethe interference state in the specific frequency band, in much the sameway as in step S104. The UE 100 may regularly perform the carrier senseon the basis of the configuration information from the PCell, and maystart the carrier sense if reception quality from the U-SCell is lowerthan a threshold value.

In the present embodiment, description proceeds with an assumption thatthe UE 100 that has performed the carrier sense has determined that thesecond and third channels are free channels.

In step S112, the UE 100 transmits (i.e., notifies), to the PCell or thepSCell, the measurement report in much the same way as in step S105. Ifreceiving the measurement report, the pSCell (SeNB) notifies the PCell(MeNB) of the measurement report.

In step S113, in much the same way as in step S106, a USCell that hasperformed the carrier sense notifies the PCell of the measurementreport. In the present embodiment, description proceeds with anassumption that the U-SCell has notified, as the measurement report,free channel information ({1,0,0,1}) indicating that the first andfourth channels are free channels.

In step S114, the PCell determines, on the basis of the measurementreport acquired in each of steps S112 and S113, that the first to fourthchannels are used channels and thus there is no free channel. Ifdetermining that there is no free channel, the Pcell stops theallocation of the time-frequency resource to UE 100. The interferenceoccurs if the UE 100 performs the communication in the specificfrequency band, and thus, by stopping the resource allocation, it ispossible to restrain the interference to another radio device. As aresult, it is possible to effectively utilize the specific frequencyband.

It is noted that the PCell may start the communication, in which thegeneral frequency band is used, with the UE 100. Alternatively, if theUE 100 was performing the communication by utilizing the generalfrequency band as well as the specific frequency band, the PCell maycontinue the communication, in which the general frequency band isutilized, with the UE 100.

In step S115, the PCell transmits a U cell end message (U-cellDeactivate) to the UE 100. The UE 100 that has received the U cell endmessage, ends the communication with the U-SCell. Specifically, the UE100 ends transmission to the U-SCell (uplink transmission), and ends thedownlink monitoring. Further, if not communicating with the U-SCellother than the U-SCell instructed by the U cell end message (if there isno activated U-SCell), the UE 100 may turn the radio transceiver 110B toOFF. The UE 100 is capable of holding a configuration regarding theU-SCell with which the communication was being performed.

It is noted that step S115 may be omitted.

In step S116, the UE 100 ends the carrier sense. The UE 100 may end thecarrier sense in response to reception of the U cell end message.Alternatively, the UE 100 may end the carrier sense if not receiving theresource allocation from the Pcell.

(Modification 1-1)

Next, an operation according to a modification 1 (modification 1-1) ofthe first embodiment will be described by using FIG. 8. FIG. 8 is asequence diagram for describing the operation according to themodification 1 of the first embodiment. The modification 1 is theStandalone with LAA case. The notification between the MeNB (PCell) andthe SeNB (U-SCell including U-pSCell) is performed via a backhaul (withor without wires) between the eNBs 200.

Description overlapping the above-described embodiment is omitted, whereappropriate.

As illustrated in FIG. 8, in step S201, the Pcell transmits, to the eNBconfigured to manage a cell that may be the U-pSCell or the U-SCell, aU-SeNB addition message (U-SeNB Addition) for requesting addition of acell of the specific frequency band in order to perform communicationwith the UE 100.

In step S202, the eNB that has received the U-SeNB addition messagestarts the carrier sense for measuring the interference state in thespecific frequency band (see step S106). The eNB determines whether ornot it is possible to add a cell of the eNB as the U-pSCell or theU-SCell (hereinafter, U-pSCell). If there is the free channel, on thebasis of the measurement result, the eNB determines that it is possibleto add, as the U-pSCell, a cell of the eNB for communication with the UE100. In the present embodiment, description proceeds with an assumptionthat the eNB 200 has determined that it is possible to add, as theU-pSCell, a cell of the eNB.

In step S203, the eNB transmits, to the PCell, a U-SeNB additionresponse message (U-SeNB Addition Response) indicating whether or not itis possible to add, as the U-pSCell, a cell of the eNB.

In the present embodiment, in order to add a cell of the eNB as theU-pSCell, the eNB 200 transmits the U-SeNB addition response message.The U-SeNB addition response message includes information necessary toadd a cell of the eNB as the U-pSCell.

Description proceeds while the operation of the eNB 200 is regarded asthe operation of the U-pSCell, below.

Step S204 corresponds to step S101.

In step S205, the U-pSCell transmits the U-cell activation message tothe UE 100 (see step S102). It is noted that U-cell activation messagemay be transmitted from the PCell.

Steps S206 to S208 correspond to steps S103 to S105.

In step S209, the PCell utilizes the general frequency band to transfer,via the backhaul, the measurement report received from the UE 100.Accordingly, the UE 100 notifies, by way of the PCell, the U-pSCell(SeNB) of the measurement report. By utilizing the general frequencyband and the backhaul rather than the specific frequency band, it ispossible to ensure that the measurement report is notified from the UE100 to the U-pSCell without causing interference to the other radiodevice that perform communication in the specific frequency band.

In step S210, (a scheduling control device of) the U-pSCell performsscheduling to allocate the time-frequency resource to the UE 100 (seestep S107). The U-pSCell allocates, if receiving, from the PCell, theinformation instructing a timing at which the UE 100 measures theinterference state, the time-frequency resource so that the UE 100 doesnot perform the exchange at the timing.

It is noted that the U-pSCell may utilize the measurement resultobtained in step S202, and may utilize the measurement result obtainedas a result of performing the carrier sense after transmitting theU-cell activation message in S205, or after acquiring the measurementreport of the UE 100 in S209.

In step S211, the U-pSCell or the U-SCell transmits, to the UE 100, theresource allocation (Resource Allocation) in step 210 by the PDCCH (seestep S109).

Steps S212 and S213 correspond to steps S110 and S112.

In step S214, in much the same way as in step S209, the PCell utilizesthe general frequency band to transfer, via the backhaul, themeasurement report received from the UE 100. Accordingly, it is possibleto restrain the interference to the other radio device.

Further, the U-pSCell starts the carrier sense in much the same way asin step S202. As a result, the U-pSCell acquires the measurement resultindicating the interference state in the specific frequency band.

In step S215, if determining, on the basis of the measurement resultobtained in step S214 and the measurement result of itself, that thereis no free channel, the U-pSCell stops the allocation of thetime-frequency resource to the UE 100 (see step S114).

(Modification 1-2)

Next, an operation according to a modification 2 (modification 1-2) ofthe first embodiment will be described by using FIG. 9. FIG. 9 is asequence diagram for describing the operation according to themodification 2 of the first embodiment. The modification 2 is theStandalone case. If the CA is utilized, below, the U-Cell includes atleast any one of the U-SCell and the U-PCell. Description overlappingthe above-described embodiment and modification 1 is omitted, whereappropriate.

As illustrated in FIG. 9, in step S301, the U-Cell starts the carriersense for measuring the interference state in the specific frequencyband (see step S202).

In step S302, the U-Cell (U-PCell) transmits the RRC connectionreconfiguration message to the UE 100 (see step S101). It is noted thatif the U-Cell is the USCell, the RRC connection reconfiguration messageis not transmitted from the PCell not shown.

Steps S303 to S305 correspond to steps S205 to S207. It is noted that instep S303, the U-PCell or the U-SCell is capable of transmitting theU-cell activation message.

In step S306, the UE 100 transmits (i.e., notifies) a measurement report(Free channel/resource feedback) to the U-Cell (U-PCell).

Steps S307 to S309 correspond to steps S210 to S212. It is noted that instep S308, the U-PCell or the U-SCell is capable of transmitting theresource allocation to the UE 100.

In step S310, the UE 100 transmits the measurement report to the U-Cellin much the same way as in step S306.

Step S311 corresponds to step S215.

Thus, even if it is not possible to utilize the general frequency band,when the scheduling is performed by using the measurement resultindicating the interference state in the specific frequency band, theU-Cell is capable of effectively utilizing the specific frequency band.

[Second Embodiment]

Next, an operation according to a second embodiment will be described byusing FIG. 10. FIG. 10 is a sequence diagram for describing theoperation according to the second embodiment. Here, the LAA case will bedescribed.

In the above-described first embodiment, description proceeds with afocus on the operation in which the specific frequency band iseffectively utilized by performing the scheduling by using themeasurement result indicating the interference state in the specificfrequency band. In the second embodiment, description proceeds with afocus on an operation in which in order to effectively utilize thespecific frequency band, the UE 100 stops the communication if receivingthe interference in the specific frequency band and the UE 100 starts(restarts) the communication if stopping receiving the interference inthe specific frequency band.

As illustrated in FIG. 10, in step S401, the Pcell transmits the RRCconnection reconfiguration message (RRC Connection Reconfiguration) tothe UE 100.

The RRC connection reconfiguration message includes counterconfiguration information (counter config.). The counter configurationinformation is configuration information to allow the UE 100 to measurethe number of times in which reception (decoding) of data transmitted inthe specific frequency band is failed. The counter configurationinformation includes information indicating a threshold value(hereinafter, “decoding failure threshold value”) used for comparisonwith the number of times in which the data reception is failed.

In step S402, the U-SCell utilizes the specific frequency band totransmit the data to the UE 100.

In step S403, the UE 100 attempts to decode the data transmitted fromthe U-SCell. Here, description proceeds with an assumption that as aresult of successfully decoding the data, the UE 100 has properlyreceived the data by utilizing the specific frequency band.

The UE 100 transmits, to the U-SCell, an acknowledgment (ACK) indicatingthat the data has been properly received by utilizing the specificfrequency band.

In step S404, the U-SCell utilizes, in much the same way as in stepS402, the specific frequency band to transmit the data to the UE 100.

In step S405, decoding the data transmitted from the U-SCell isattempted. Here, description proceeds with an assumption that as aresult of failing to decode the data, the UE 100 has not properlyreceived the data by utilizing the specific frequency band.

In this case, the UE 100 compares the number of times in which decodingof the data transmitted in the specific frequency band is failed (or aNACK transmission count, described below) with a decoding failurethreshold value. Description proceeds with an assumption that the numberof times is less than the decoding failure threshold value.

In step S406, the UE 100 transmits a negative acknowledgment (NACK)indicating that the data has not been properly received by utilizing thespecific frequency band, to the PCell or the pSCell rather than to theU-SCell from which the data has been transmitted. Thus, in the presentembodiment, the UE 100 utilizes the specific frequency band to transmitthe ACK, and utilizes the general frequency band to transmit the NACK.As a result, even if receiving the interference in the specificfrequency band from another radio device, the UE 100 is capable ofutilizing the general frequency band so as to reliably convey to thedata transmission source that the data has not been properly received.

The PCell or the pSCell is capable of notifying the U-SCell of the NACKreceived from the UE 100. If the PCell and the U-SCell are managed bythe different eNB 200, the PCell is capable of notifying, via thebackhaul, the U-SCell of the NACK.

Thereafter, the UE 100 increments the number of times in which decodingof the data transmitted in the specific frequency band is failed (or theNACK transmission count).

In step S407, the U-SCell utilizes the specific frequency band totransmit (retransmit) the data to the UE 100. If receiving, from thePCell, a notification indicating that the NACK from the UE 100 has beenreceived, the U-SCell retransmits the data to the UE 100. Alternatively,if not capable of receiving the ACK from the UE 100 within apredetermined time, the USCell may retransmit the data to the UE 100.

In step S408, the UE 100 transmits the ACK to the USCell in much thesame way as in step S403.

In step S409, the U-SCell utilizes the specific frequency band totransmit the data to the UE 100.

In step S410, the UE 100 attempts to decode the data transmitted fromthe U-SCell in much the same way as in step S405. Here, descriptionproceeds with an assumption that as a result of failing to decode thedata, the UE 100 has not properly received the data by utilizing thespecific frequency band and the NACK transmission count reaches thedecoding failure threshold value. As a result, the UE 100 determinesthat the reception quality in the specific frequency band is lower thana threshold value.

In step S411, the UE 100 transmits the NACK to the PCell or the pSCellin much the same way as in step S406.

In step S412, the UE 100 transmits (i.e., notifies) to the PCell or thepSCell a stop request to request a stop of the communication in thespecific frequency band (Stop request), in response to the NACKtransmission count having reached the decoding failure threshold value.If the pSCell receives the stop request, the pSCell notifies the Pcellof the stop request. Thus, the UE 100 transmits the stop request byutilizing the general frequency band rather than the specific frequencyband.

In the present embodiment, the stop request is information indicatingthat the reception quality is lower than a threshold value in thespecific frequency band. As a result, even if receiving the interferencein the specific frequency band from another radio device, the UE 100 iscapable of utilizing the general frequency band so as to reliably conveythe stop request to the scheduling control device (and/or the datatransmission source).

The PCell stops, on the basis of the stop request, allocation to the UE100 of the time-frequency resource in the specific frequency band.

It is noted that the stop request is similar to a deactivation request;however, differs in that the communication with the cell that is to bestopped is not completely ended (that is, the communication istemporarily stopped).

In step S413, the PCell or the U-SCell notifies, on the basis of thestop request from the UE 100, the U-SCells of a resource allocation stopmessage (Stop resource allocation) indicating that the allocation of thetime-frequency resource to the UE 100 is stopped, and the U-SCell thathas received a notification of the resource allocation stop message iscapable of stopping the transmission (retransmission) to the UE 100.

In step S414, the UE 100 starts the carrier sense to measure theinterference state in the specific frequency band. Here, the UE 100start the carrier sense in accordance with the number of times in whichthe data has not been properly received by utilizing the specificfrequency band (NACK transmission count). In the present embodiment, theUE 100 starts the carrier sense after the NACK transmission countreaches the decoding failure threshold value.

In step S415, the UE 100 detects, by the carrier sense, a free channelin which the interference signal is less than a threshold value, in thespecific frequency band.

In step S416, if the UE 100 detects a free channel (for a predeterminedperiod) (i.e., if the interference signal is equal to or less than thethreshold value in at least a part of the specific frequency band), theUE 100 utilizes the general frequency band to transmit a restart request(Restart request) to start the communication in the specific frequencyband, to the PCell or the pSCell. If the pSCell receives the restartrequest, the pSCell notifies the Pcell of the restart request. Thus, theUE 100 transmits the restart request by utilizing the general frequencyband rather than the specific frequency band. The restart request may beinformation indicating that there is no interference.

It is noted that the restart request is similar to a re-activationrequest; however, differs from the re-activation request in that in thecell to be restarted, the communication is temporarily stopped. ThePCell restarts, on the basis of the restart request, allocation to theUE 100 of the time-frequency resource in the specific frequency band.

In step S417, the PCell or the pSCell transmits, on the basis of therestart request from the UE 100, a resource allocation restart message(Restart resource allocation) indicating restart of the allocation ofthe time-frequency resource. The PCell or the pSCell may include thetime-frequency resource in the specific frequency band allocated to theUE 100, into the resource allocation stop message.

In step S418, the U-SCell that has received the resource allocationrestart message restarts the transmission of the data to the UE 100 inwhich the specific frequency band is utilized.

(Modification 2-1)

Next, an operation according to a modification 1 (modification 2-1) ofthe second embodiment will be described by using FIG. 11. FIG. 11 is asequence diagram for describing the operation according to themodification 1 of the second embodiment. The present modificationcorresponds to the LAA case. Description overlapping each of theabove-described embodiments is omitted, where appropriate.

In the above-described second embodiment, the UE 100 determines that thereception quality in the specific frequency band is lower than thethreshold value. In the present modification, the U-SCell determinesthat the reception quality of the UE 100 in the specific frequency bandis lower than the threshold value.

In step S501, the U-SCell utilizes the specific frequency band totransmit the data to the UE 100. Here, description proceeds with anassumption that the UE 100 has successfully decoded the data transmittedfrom the U-SCell.

In step S502, the UE 100 transmits, to the PCell or the pSCell, theacknowledgment (ACK) indicating that the data has not properly receivedby utilizing the specific frequency band. In the present modification,the UE 100 transmits, to the PCell or the pSCell, not only the NACK butalso the ACK. The pSCell may notify the PCell of the ACK/NACK receivedfrom the UE 100.

In step S503, the U-SCell utilizes, in much the same way as in stepS501, the specific frequency band to transmit the data to the UE 100.Here, description proceeds with an assumption that the UE 100 has failedto decode the data transmitted from the U-SCell.

In step S504, the UE 100 transmits, to the PCell or the pSCell, thenegative acknowledgment (NACK) indicating the it was not possible tohave properly received the data by utilizing the specific frequency band(see step S406). It is noted that the PCell or the pSCell counts a NACKreception count, and compares the reception count with a thresholdvalue. Here, description proceeds with an assumption that the receptioncount is less than the threshold value.

Steps S505 and S506 correspond to steps S503 and S504.

In step S507, the PCell or the pSCell determines, if the NACK receptioncount has reached the threshold value, that the reception quality of theUE 100 in the specific frequency band is lower than the threshold value.In this case, the PCell executes the processes of steps S509 and S511.It is noted that if the pSCell makes the determination, an indicationthat the reception quality of the UE 100 in the specific frequency bandis lower than the threshold value may be notified to the PCell.

It is noted that the threshold value in this case may be the same as thedecoding failure threshold value included in the counter configurationinformation in step S401.

In step S508, the PCell or the pSCell transmits, to the UE 100, ameasurement instruction (Carrier Sense Indication) of the interferencestate in the specific frequency band by utilizing the general frequencyband. Thus, the UE 100, which is not capable of reception by utilizingthe specific frequency band, is capable of receiving the measurementinstruction. The measurement instruction may include informationindicating a channel (frequency band) used for the resource allocationto the UE 100.

It is noted that in order to grasp a radio condition in the specificfrequency band of a whole of the coverage of the PCell, the PCell or thepSCell may transmit the measurement instruction not only to the UE 100but also to another UE in the coverage of the PCell.

In step S509, the PCell or the pSCell notifies the U-SCell of atransmission stop instruction (Stop Transmission Indication) that is aninstruction to ensure that the data transmission (retransmission) to theUE 100 is stopped.

In step S510, the U-SCell stops, on the basis of the transmission stopinstruction, the transmission (retransmission) to the UE 100.

In step S511, the PCell stops, in accordance with the reception state ofthe NACK from the UE, the allocation of the time-frequency resource inthe specific frequency band to the UE 100. Specifically, the PCell stopsthe resource allocation to the UE 100 after the NACK reception count hasreached the threshold value.

In step S512, the UE 100 starts, on the basis of the measurementinstruction of step S508, the carrier sense for measuring theinterference state in the specific frequency band. If the measurementinstruction of step S508 includes information indicating a channel(frequency band) used for the resource allocation to the UE 100, themeasurement of the interference state may be performed on the channel.

It is noted that the U-SCell may start the carrier sense after stoppingthe transmission (retransmission) to the UE 100.

In step S513, if the U-SCell detects a free channel (for a predeterminedperiod), the U-SCell may notify, in step S514, the PCell of a restartrequest (Restart request) to start the communication in the specificfrequency band.

Steps S515 to S518 correspond to steps S415 to S418.

It is noted that in step S517, if receiving the restart request not onlyfrom the UE 100 but also from the U-SCell, the PCell may notify theU-SCell of the resource allocation restart message.

(Modification 2-2)

Next, an operation according to a modification 2 (modification 2-2) ofthe second embodiment will be described by using FIG. 12. FIG. 12 is asequence diagram for describing the operation according to themodification 2 of the second embodiment. The present modificationcorresponds to the Standalone with LAA case. Description overlappingeach of the above-described embodiments is omitted, where appropriate.

The present modification presents, in much the same way as in theabove-described second embodiment, a case where the UE 100 determinesthat the reception quality in the specific frequency band is lower thanthe threshold value.

As illustrated in FIG. 12, in step S601, the PCell (MeNB) transmits, tothe UE 100, an RRC connection reconfiguration message (RRC ConnectionReconfiguration) (see step S401).

Steps S602 to S605 correspond to steps S402 to S405.

In step S606, the UE 100 transmits the NACK to the U-pSCell.

In step S607, the U-pSCell (and the U-SCell) transmits (retransmits) thedata to the UE 100, in accordance with the NACK.

Steps S608 to S610 correspond to steps S408 to S410.

In step S611, the UE 100 transmits, in much the same way as in stepS606, the NACK to the U-pSCell.

In step S612, the UE 100 transmits (notifies), in accordance with theNACK transmission count having reached the decoding failure thresholdvalue, the stop request (Stop request) to the PCell rather than to theU-pSCell to which the ACK/NACK is transmitted.

In step S613, the PCell that has received the stop request transfers thereceived stop request, via the backhaul, to the U-pSCell or the U-SCell.As a result, the UE 100 notifies, by way of the PCell, the U-pSCell orthe U-SCell of the stop request. By utilizing the general frequency bandand the backhaul rather than the specific frequency band, it is possibleto ensure that the stop request is notified from the UE 100 to theU-pSCell or the U-SCell without causing interference to another radiodevice that performs communication in the specific frequency band.

Steps S614 to S616 correspond to steps S414 to S416.

In step S617, the PCell that has received the restart request transfersthe received restart request, via the backhaul, to the U-pSCell or theU-SCell. As a result, the UE 100 notifies, by way of the PCell, theU-pSCell or the U-SCell of the stop request. By utilizing the generalfrequency band and the backhaul rather than the specific frequency band,it is possible to ensure that the restart request is notified from theUE 100 to the U-pSCell or the U-SCell without causing interference toanother radio device that performs communication in the specificfrequency band.

Step S618 corresponds to step S418.

(Modification 2-3)

Next, an operation according to a modification 3 (modification 2-3) ofthe second embodiment will be described by using FIG. 13. FIG. 13 is asequence diagram for describing the operation according to themodification 3 of the second embodiment. The present modificationcorresponds to the Standalone with LAA case. Description overlappingeach of the above-described embodiments is omitted, where appropriate.

In the modification 1 of the above-described second embodiment, thePCell (or the pSCell) determines that the reception quality of the UE100 in the specific frequency band is lower than the threshold value. Inthe present modification, the U-pSCell or the U-SCell determines thatthe reception quality of the UE 100 in the specific frequency band islower than the threshold value.

In step S701, the PCell may transmit the counter configurationinformation to the U-pSCell or the U-SCell (see step S401). It is notedthat step S701 may be omitted. In this case, the U-pSCell may use apreset threshold value (decoding failure threshold value).

Steps S702 to S707 correspond to steps S602 to S604, S606, S609, andS611.

In step S708, the U-pSCell determines, if the NACK reception count hasreached the threshold value, that the reception quality of the UE 100 inthe specific frequency band is lower than the threshold value (see stepS507). In this case, the U-pSCell performs processes of steps S709 andS710.

Further, (a scheduling control device of) the U-pSCell stops theallocation to the UE 100 of the time-frequency resource in the specificfrequency band.

It is noted that the U-pSCell may replace the number of times in whichit is not possible to receive the ACK within a predetermined time by thenumber of times in which the NACK is received.

In step S709, the U-pSCell (or the U-SCell) notifies, via the backhaul,the PCell of a transmission error instruction, as the informationindicating that the reception quality of the UE 100 in the specificfrequency band is lower than a threshold value. The transmission errorinstruction may include information indicating a channel (frequencyband) used for the resource allocation to the UE 100.

Steps S710 and S711 correspond to (the operation of the U-SCell of)steps S510 and S512.

Step S712 corresponds to step S508. Here, the PCell transmits, on thebasis of the transmission error instruction from the U-pSCell (or theU-SCell), the measurement instruction to the UE 100 by utilizing thegeneral frequency band. Therefore, the transmission error instruction isused as a trigger for causing the UE 100 to start the carrier sense. TheUE 100 is capable of reliably receiving the measurement instructionbecause of routing the general frequency band, even if the interferenceoccurs in the specific frequency band.

Steps S713 to S718 correspond to steps S513 to S518.

(Modification 2-4)

Next, an operation according to a modification 4 (modification 2-4) ofthe second embodiment will be described by using FIG. 14. FIG. 14 is asequence diagram for describing the operation according to themodification 4 of the second embodiment. The present modificationcorresponds to the Standalone case. Description overlapping each of theabove-described embodiments is omitted, where appropriate.

In the present modification, each of the U-Cell and the UE 100determines that the reception quality of the UE 100 in the specificfrequency band is lower than the threshold value.

As illustrated in FIG. 14, in step S801, the U-Cell (the U-PCell or theU-SCell) transmits threshold value configuration information (Thresholdconfig.) to the UE 100. The threshold value configuration informationmay include the following information.

-   -   Information indicating the decoding failure threshold value (see        step S401)    -   Information indicating a retransmission timer (T-retransmission)    -   Information indicating the retransmission count        (N-retransmission)

The UE 100 sets information included in the threshold valueconfiguration information. When the threshold value configurationinformation includes the information indicating the decoding failurethreshold value, the U-Cell and the UE 100 are capable of sharing thedecoding failure threshold value.

Step S802 to step S807 correspond to step S702 to step S707. It is notedthat the U-Cell (the U-PCell or the U-SCell) counts the NACK receptioncount (or an ACK reception failure count), and each of the UEs 100counts the NACK transmission count. The U-Cell and the UE 100 comparethe counted count with the decoding failure threshold value.

Steps S808 and S809 correspond to steps S410 and S414. Steps S810 toS813 correspond to steps S708, S710, S711, and S713. Steps S814 and S815correspond to steps S415 and S416.

In step S816, if the UE 100 sets a retransmission timer, theretransmission timer is started on the basis of transmission of theretransmission request of step S815. It is noted that the retransmissiontimer may be started by using, as a trigger, the transmission of theretransmission request by using the specific frequency band withoututilizing the general frequency band. This is due to the fact that thespecific frequency band is available without a license, and as comparedwith the general frequency band, it is highly likely that the U-Cell isnot capable of receiving the retransmission request.

In step S817, the U-Cell that has received the retransmission request ofstep S815 restarts the transmission of the data to the UE 100 that hasutilized the specific frequency bands. The U-Cell may restart thetransmission of the data to the UE 100, if detecting, in S813, a freechannel (for a predetermined period), in addition to the retransmissionrequest from the UE 100.

In step S818, if the retransmission timer has been started, the UE 100stops the retransmission timer in response to the reception of the datafrom the UCell.

On the other hand, in step S819, if the retransmission timer expiresbefore receiving the data from the U-Cell, in step S820, the UE 100retransmits the retransmission request. Then, the retransmission timermay be started. The UE 100, which sets the retransmission count, endsthe retransmission of the retransmission request if it is not possibleto receive the data from the U-Cell even after the retransmission countis exceeded.

[Other Embodiments]

In each of the above-described embodiments, an eNB 200 configured tomanage the general frequency band and an eNB 200 configured to managethe specific frequency band, may be the same or different. Further, inthe above embodiments, if the eNB 200 configured to manage the generalfrequency band and the eNB 200 configured to manage the specificfrequency band are different, it is possible to use an X1 interface oran S1 interface for exchange of a signal between a cell in which thegeneral frequency band is utilized (e.g., the PCell) and a cell in whichthe specific frequency band is utilized (e.g., the U-Scell). Further,the backhaul may be with or without wires.

Further, in each of the above-described embodiments, the configurationinformation transmitted by the PCell to the UE 100 may include thefollowing information.

-   -   Special cell information indicating a special cell in the        specific frequency band    -   Period information indicating a period during which the UE 100        measures the interference state

The UE 100 is capable of determining that it is necessary to measure theinterference state or determining to perform communication by using aWLAN link, in response to the reception of the special cell information.

The UE 100 does not fail to measure the interference state within aperiod (once) indicated by the period information. The UE 100 maymeasure the interference state in a period indicated by the periodinformation.

In the above-described second embodiment, if a split bearer has beenestablished, the MeNB (PCell) may determine whether or not to transferthe data of the UE 100 to the SeNB on the basis of the measurementreport from the UE 100 and the measurement report from the SeNB(U-pSCell) after receiving the measurement report from the UE 100 instep S208. If there is a free channel, the PCell may start the transferof the data of the UE 100 to the U-SCell. In this case, if determiningon the basis of the measurement report from the UE 100 in S213 thatthere is no free channel, the MeNB may stop the transfer of the data ofthe UE 100 to the SeNB.

It is noted that in the split-bearer, in the DC, in order to use theresources of both the MeNB and the SeNB, a radio protocol of the beareris located in both the MeNB and the SeNB. In split bearer, a split isobserved in the MeNB 200-1 between the UE 100 and the P-GW, one of thesplits (split bearer) is terminated in the UE 100 after passing throughthe SeNB 200-2, and the other split (split bearer) is terminated in theUE 100 without passing through the SeNB 200-2.

In the above-described second and third embodiments, the UE 100transmits, in response to the NACK transmission count having reached thedecoding failure threshold value, the stop request to the PCell or thepSCell; however, this is not limiting. The UE 100 may transmit the stoprequest if the data decoding failure count reaches the threshold value(decoding failure threshold value) in spite of the NACK transmissioncount.

In the above-described second and third embodiments, the UE 100transmits the stop request to the PCell or the pSCell; however, this isnot limiting. The UE 100 may transmit, instead of the stop request, anotification indicating that the data decoding failure count reaches anupper limit value to the PCell or the pSCell.

Further, in each of the above-described embodiments, instead of the eNB,e.g., an RRH base station (Remote Radio Head) may manage the specificfrequency band and/or the general frequency band. In this case, insteadof the backhaul, a fronthaul that connects an RRH and a BBH (Base BandUnit) may be used to notify the information to another RRH.

Further, the eNB configured to manage the specific frequency band may becollocated with the eNB configured to manage the general frequency band(a macro cell or a small cell), and may be collocated with a wirelessLAN access point.

Further, in each of the above-described embodiments, the UE 100 maytransmit the ACK/NACK by utilizing the specific frequency band if a datareception state in which the specific frequency band is utilized isequal to or greater than a threshold value, and may transmit theACK/NACK by utilizing the general frequency band if the reception stateis less than the threshold value. Alternatively, the UE 100 may utilizeboth the specific frequency band and the general frequency band totransmit the ACK/NACK.

In each of the above-described embodiments, in the Standalone with LAAcase, the UE 100 has received the data from the U-pSCell and theU-SCell; however, this is not limiting. The UE 100 may receive the datafrom the U-pSCell only. Alternatively, the UE 100 may receive the datafrom a cell (U-PCell) in which the specific frequency band is managed bythe MeNB. In this case, the MeNB manages the PCell and the U-PCell.

Further, in each of the above-described embodiments, the Standalone casemay be a case where the specific frequency band in the DC may beutilized as the cell (U-PCell) managed by the MeNB and the cell(U-pSCell, U-SCell) managed by the SeNB.

In the above-described embodiments, although the LTE system is describedas an example of the mobile communication system, it is not limited tothe LTE system, and the present application may be applied to a systemother than the LTE system.

INDUSTRIAL APPLICABILITY

As described above, the mobile communication system, the user terminal,the base station, the processor, and the communication control methodaccording to the present embodiment are useful in the mobilecommunication field because it is possible to effectively utilize aspecific frequency band.

The invention claimed is:
 1. A user terminal configured to communicateby using an unlicensed frequency band, comprising: a receiver; and acontroller; wherein the receiver is configured to receive, from a basestation, a message including first information and second information,the first information is information regarding to a configuration forreporting a power measured by the user terminal in the unlicensedfrequency band, the first information includes period informationindicating a period of a measurement in the unlicensed frequency band,the second information is information regarding to a configuration ofcarrier aggregation, and the controller is configured to: periodicallymeasure the power in the unlicensed frequency band according to theperiod information; report to the base station on information classifiedaccording to the measured power as information indicating the measuredpower, on a basis of the first information; perform a configuration forusing the unlicensed frequency band as a secondary carrier in thecarrier aggregation, on a basis of the second information; andcommunicate a communication with the base station by using the secondarycarrier, and the controller is configured: to perform a control to startthe communication of the unlicensed frequency band, in response to areception of third information indicating that the communication of theunlicensed frequency band is allowed, wherein the third informationdiffers from the first information and the second information; and notto perform the control until the reception of the third information eventhough the receiver receives the message including the first informationand the second information.
 2. A processor for controlling a userterminal configured to communicate by using an unlicensed frequencyband, the processor configured to: receive a message including firstinformation and second information, the first information is informationregarding to a configuration for reporting a power measured by the userterminal in the unlicensed frequency band, the first informationincludes period information indicating a period of a measurement in theunlicensed band, the second information is information regarding to aconfiguration of carrier aggregation, and the processor is configuredto: periodically measure the power in the unlicensed frequency bandaccording to the period information; report to a base station oninformation classified according to the measured power as informationindicating the measured power, on a basis of the first information;perform a configuration for using the unlicensed frequency band as asecondary carrier in the carrier aggregation, on a basis of the secondinformation; and communicate a communication with the base station byusing the secondary carrier, the processor is further configured: topreform a control to start the communication of the unlicensed frequencyband, in response to a reception of third information that thecommunication of the unlicensed frequency band is allowed, wherein thethird information differs from the first information and the secondinformation; and not to preform the control until the reception of thethird information even though the receiver receives the messageincluding the first information and the second information.